This invention relates generally to golf balls including a core having at least one wound layer and a cover disposed thereabout, and more particularly to wound golf balls having a wound thread layer between rubber-based layers.
Conventional golf balls can be divided into two general types of groups: solid balls or wound balls. The difference in play characteristics resulting from these different types of construction can be quite significant. Balls having a solid construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Solid balls are generally made with a single solid core, which is enclosed by a cover material. Typically the solid core is made of polybutadiene which is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents. The cover is generally a material such as SURLYN(copyright), which is a trademark for an ionomer resin produced by DuPont. Because these materials are very rigid, solid balls can have a hard xe2x80x9cfeelxe2x80x9d when struck with a club. Likewise, due to their construction, these balls have a relatively low spin rate which provides greater distance.
At the present time, the wound ball provides the advanced player better spin and feel characteristics. Wound balls typically have either a spherical solid rubber or liquid center core around which many yards of a tensioned elastic thread are wound. The wound core is then covered with a durable cover material, such as a SURLYN(copyright) or similar material, or a softer cover such as Balata or polyurethane. Wound balls are generally softer and provide more spin, which enables a skilled golfer to have more control over the ball""s flight and position. Particularly, with approach shots onto the green, the high spin rate of soft, wound balls enable the golfer to stop the ball very near its landing position.
Regardless of ball construction, players generally seek a golf ball that maximizes total game performance for their requirements. Therefore, in an effort to meet the demands of the marketplace, manufacturers strive to produce golf balls with a wide variety of performance characteristics to meet the players individual requirements. Thus, golf ball manufacturers are continually searching for new ways in which to provide golf balls that deliver the maximum performance for golfers of all skill levels.
To meet the needs of golfers with various levels of skill, golf ball manufacturers are also concerned with varying the level of the compression of the ball, which is a relative measurement of the golf ball stiffness under a fixed load. A ball with a higher compression feels harder than a ball of lower compression. Wound golf balls generally have a lower compression which is preferred by better players. Whether wound or solid, golf balls typically become more resilient (i.e., have higher initial velocities) as compression increases. Manufacturers of both wound and solid construction golf balls must balance the requirement of higher initial velocity resulting from a higher compression with the desire for a softer feel from lower compression.
To make wound golf balls, manufacturers use winding machines to stretch the threads to various degrees of elongation during the winding process without subjecting the threads to unnecessary incidents of breakage. Generally, as the elongation and winding tension increase, the compression and initial velocity of the ball increase. Thus, a more resilient wound ball is produced, which is desirable.
Referring to FIG. 1, a conventional golf ball thread 10 is shown. In general, a single-ply golf ball thread or two-ply thread 10 is formed and wound around a center. Single-ply threads are generally made using a liquid latex that is cast into a sheet and then slit into threads having a generally rectangular or square cross-section. Two-ply threads are generally made by mixing synthetic cis-polyisoprene rubbers, natural rubber and a curing system together, calendering this mixture into two sheets, calendering the sheets together, curing the sheets to vulcanize and bond the sheets together, and slitting the resultant sheet into threads having a generally rectangular or square cross-section. Another method of forming threads is through an extrusion process. Extruded thread, however, has not previously been used in golf ball applications. An example of an extruded thread that is not used in golf balls is disclosed in U.S. Pat. No. 5,679,196 to Wilhelm et al. This patent discloses a thread formed from a mixture having more than 50 percent natural rubber.
A number of different windings have been disclosed for use in golf balls. U.S. Pat. No. 4,473,229 to Kloppenburg et al. discloses a golf ball having a core formed of graphite fibers and windings made of graphite filaments and resins. Yarns are made with the graphite filaments and resins, and as many as four or more yarns are combined to form a final yarn used for winding. U.S. Pat. No. 5,713,801 to Aoyama discloses the use of a layer of high tensile elastic modulus fibers wound about the core. The fibers have a tensile elastic modulus of at least 10,000 kpsi. Also, U.S. Pat. No. 5,816,939 to Hamada et al. discloses a rubber thread for winding with a tensile strength retention of up to 70 percent, a hysteresis loss of at least 50 percent, and an elongation of 900 percent to 1400 percent.
Prior art wound golf balls and cores typically use polyisoprene rubber thread. The polyisoprene thread is wound onto the cores at elongations between 500 percent to 1000 percent. The amount of thread required for a golf ball core is dependent on the elastic modulus of the thread in the elongated state. Elongated polyisoprene thread has an elastic modulus between 10,000 psi and 20,000 psi. Further, the properties, in particular resilience, of the wound ball or core are dependent on how well the thread packs during winding. The dimensions of the thread control the packing density. Polyisoprene threads are typically 0.0625 inches wide by 0.02 inches thick, measured prior to winding. However, present art polyisoprene thread is commonly produced in thicknesses between 0.014 inches and 0.024 inches.
There are some drawbacks to the conventional single-ply threads used in golf balls. The single-ply occasionally contains weak points. As a result, manufacturers of wound balls do not wind using the maximum tension or stretch the thread to the maximum elongation, because to do so would cause an excessive amount of breakage during winding. When a thread breaks during manufacturing, an operator must restart the operation. This decreases production, and is thus undesirable. The use of two-ply threads in golf balls reduces but does not eliminate this problem.
The thread can also break during play due to impact of a club with the ball. These breaks can result in various consequences. Cover material is disposed around the thread portions adjacent the cover. When the thread portions adjacent the cover break, the cover material tends to hold these thread portions in the proper position. If enough thread portions break near the cover, however, a lump will be created on the outside surface of the ball, which makes the ball unplayable.
More severe problems can occur, however, when thread portions near the center break. In a wound ball with a solid rubber center, the resilient rubber of the center is relatively soft compared to the hardness of the highly stretched thread portions. After a thread portion adjacent the center breaks, the thread portion can contract and cause a loss of compression and resiliency. This results in an undesirable distance loss.
In a wound ball with a fluid-filled center, after a thread portion adjacent the center breaks, the resultant imbalance in stress adjacent the center causes the thread to cut through the envelope that contains the fluid. This destroys the structural integrity of the ball and makes it unplayable. If this type of failure happens during a shot, it can result in a short shot. It can also result in the ball deviating from its line of flight as it leaves the club, so that the ball can end up off of the fairway. Both of these consequences are undesirable.
Therefore, golf ball manufacturers are continually searching for new ways in which to provide wound golf balls that deliver the maximum performance for golfers while decreasing the occurrence of thread breaks both during manufacturing and during play. It would be advantageous to provide a wound golf ball with a lower compression, higher initial velocity, more dense packing, improved durability, and improved manufacturing processibility. The present invention provides such a wound golf ball.
The invention relates to a golf ball including a solid center, at least one wound thread layer disposed about the center, an intermediate layer including at least one thermoset material disposed about the wound layer, and a cover of at least one layer. In one embodiment, the wound thread layer is made of material selected from the group consisting of polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide), or polyisoprene. In another embodiment, the center has a diameter of at least about 1 inch, preferably about 1 inch to about 1.55 inches.
In another embodiment, the thread is wound at elongations of at least about 100 percent, preferably at least about 200 percent. In another embodiment, the thread has a wound elastic modulus of about 20,000 psi to about 50,000 psi. In still another embodiment, the thickness of the wound layer is less than about 0.2 inches. In yet another embodiment, the center includes polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber. In another embodiment, the at least one intermediate layer has a thickness of less than about 0.15 inches. Preferably, is made of thermoset material including at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber. More preferably, the intermediate material further includes trans-polyisoprene, trans-polybutadiene, or a mixture thereof.
The invention also relates to a golf ball including a center having a diameter of at least about 1 inch, a polymer thread wound about the center, wherein the thread includes at least one polyether urea, polyester urea, polyester block copolymers, polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide), or polyisoprene, an intermediate thermoset layer, and a cover.
In one embodiment, the thread is wound at elongations of at least about 100 percent, preferably at least about 200 percent. In one embodiment, the thread has a wound elastic modulus of about 5,000 psi to about 50,000 psi. In yet another embodiment, the diameter of the center is about 1 inch to about 1.55 inches. In a preferred embodiment, the center includes at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber.
In another embodiment, the wound thread layer including strands having cross-sectional areas less than about 0.001 in2, preferably less than about 0.0001 in2.
The present invention also relates to a golf ball including a solid center, at least one wound thread layer disposed about the center, wherein the thread is wound at an elongation of at least 100 percent or greater, preferably 200 percent or greater and includes a plurality of individual strands, an intermediate layer disposed about the at least one wound thread layer, and a cover.
In one embodiment, the at least one wound thread layer is formed from a material including polyether urea, polyester urea, polyester block copolymers, polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide), or polyisoprene. The thread preferably includes about 10 individual strands or greater. In another embodiment, the thread includes about 50 individual strands or greater.
The wound thread preferably has an elastic modulus of about 20,000 psi to about 50,000 psi. In one embodiment, the thickness of the at least one wound thread layer is about 0.2 inches or less.
In one embodiment, the golf ball includes an additional thread layer disposed about the at least one wound thread layer, wherein the additional thread layer includes a single-ply or a two-ply thread.
The intermediate layer preferably includes at least one thermoset material. The at least one thermoset material may include at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber. In one embodiment, the at least one thermoset material includes trans-polyisoprene, trans-polybutadiene, or mixtures thereof.
The solid center may include at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber, and preferably has a diameter from about 1 inch to about 1.55 inches.
In one embodiment, the cover layer includes at least one of a castable reactive liquid material, thermoset urethane ionomer, thermoset urethane epoxy, or a mixture thereof. The castable reactive liquid material is preferably a thermoset material, more preferably a thermoset cast polyurethane.
The present invention also relates to golf ball including a center, a polymer thread wound layer about the center, wherein the thread includes about 10 individual strands or greater, an intermediate layer disposed about the polymer thread wound layer, wherein the intermediate layer has a thickness of about 0.15 inches or less, and a cover.
The polymer thread may include at least one of polyether urea, polyester urea, polyester block copolymers, polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide), or polyisoprene. In one embodiment, the polymer thread is wound at an elongation of at least about 100 percent. In another embodiment, the wound polymer thread has an elastic modulus of about 20,000 psi to about 50,000 psi. The cross-sectional area of the polymer thread is preferably about 0.001 in2 or less, more preferably about 0.00001 in2 or less.
The intermediate layer and center preferably includes at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber. In one embodiment, the center has a diameter of about 1 inch to about 1.55 inches.
In another embodiment, the cover layer includes an inner cover layer and an outer cover layer, preferably wherein the inner cover layer is formed of a material having a flexural modulus of about 65,000 psi or greater and the outer cover layer includes at least one castable reactive liquid material.
The present invention is also related to a golf ball including a center, a wound thread layer disposed about the center, wherein the thread includes at least one polyether urea, polyester urea, polyester block copolymers, polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide), or polyisoprene, an intermediate layer disposed about the wound thread layer, and a cover disposed about the intermediate layer.
In one embodiment, the wound thread layer includes strands having cross-sectional areas of less than about 0.001 in2. In another embodiment, the thread is wound at an elongation of at least about 100 percent, has an elastic modulus in the wound state of about 20,000 psi to about 50,000 psi, or both.
The center and the intermediate layer preferably include at least one of polybutadiene, natural rubber, polyisoprene, styrene-butadiene, styrene-propylene-diene rubber, or mixtures thereof.
In one embodiment, the diameter of the center is about 1.2 inches to about 1.55 inches and the intermediate layer has a thickness of about 0.15 inches or less.
In one embodiment, the cover includes an inner cover layer including at least one material having a flexural modulus of about 65,000 psi or greater, preferably about 70,000 psi to about 120,000 psi and an outer cover layer disposed about the inner cover layer including at least one castable reactive liquid material, preferably a thermoset cast polyurethane. The at least one material of the inner cover layer preferably includes an ionomer resin having a methacrylic acid content of about 19 percent. The at least one castable reactive liquid material of the outer cover layer preferably has a hardness of about 30 Shore D to about 60 Shore D and a thickness of about 0.05 inches or less.